[PATCH 0/2] fix MAP_DROPPABLE not supported errno

Anthony Yznaga
2026-04-02T00:34:30Z

Mark Brown reported seeing a regression in -next on 32 bit arm with the
mlock selftests. Before exiting and marking the tests failed, the following
message was logged after an attempt to create a MAP_DROPPABLE mapping:

Bail out! mmap error: Unknown error 524

It turns out error 524 is ENOTSUPP which is an error that userspace is not
supposed to see, but it indicates in this instance that MAP_DROPPABLE is
not supported.

The first patch changes the errno returned to EOPNOTSUPP. The second patch
is a second version of a prior patch to introduce selftests to verify
locking behavior with droppable mappings with the additonal change to skip
the tests when MAP_DROPPABLE is not supported.

Anthony Yznaga (2):
mm: fix mmap errno value when MAP_DROPPABLE is not supported
selftests/mm: verify droppable mappings cannot be locked

mm/mmap.c | 2 +-
tools/testing/selftests/mm/mlock2-tests.c | 91 ++++++++++++++++++++---
2 files changed, 83 insertions(+), 10 deletions(-)

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2.47.3